joletabey is wanting to know the HOW in a breeding a project like this. I will try again .
You get a Lavender Ameraucana and breed that to a Black ORPINGTON, then take the offspring, which are F-1's, those F-1's that have a single comb you will keep to breed to each other. Within a few generations you should be able to see more Orpington type IF you know what the standard is that you are breeding too. It will take years before you completely breed out the characteristics of the Ameraucanas.
This is the " H O W " that joletabey is asking. I am sure joletabey knows how to buy eggs and birds. And yes that is an easier route. BUT, unless the birds she is buying has the Orpington type, it is not an Orpington. joletabey will have just as long a project as he/she would have buying a non finished project bird from someone else. And this is not a bad question to know the answer of "HOW people breed project birds". This is how it is described to me by someone who is doing several ORPINGTON color projects. I hope this helps.